Quarterback Alex Smith leaves the field after a game against the visiting Detroit Lions at Candlestick Park in San Francisco, Calif. on Sunday, Sept. 16, 2012. The Niners defeated the Lions 27-19.

Photo: Stephen Lam, Special To The Chronicle

Quarterback Alex Smith leaves the field after a game against the...

Quarterback Alex Smith leaves the field after a game against the... Photo-3477302.49316 - SFGate

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San Francisco 49ers quarterback Colin Kaepernick (7) and quarterback Alex Smith (11) warm up before an NFL football game against the New Orleans Saints at the Louisiana Superdome in New Orleans, Sunday, Nov. 25, 2012.

Alex Smith got his nose bloodied after a run that was called back on a penalty in the fourth quarter. The San Francisco 49ers defeated the Detroit Lions 27-19 at Candlestick Park Sunday September 16, 2012.

Photo: Brant Ward, The Chronicle

Alex Smith got his nose bloodied after a run that was called back...

Alex Smith got his nose bloodied after a run that was called back... Photo-3477294.49316 - SFGate

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49ers head coach Jim Harbaugh hugs quarterback Alex Smith after a touchdown against the Buffalo Bills at Candlestick Park in San Francisco, Calif., on Sunday, Oct. 7th, 2012.

San Francisco 49ers head coach Jim Harbaugh meets with quarterback Alex Smith (11) and quarterback Colin Kaepernick (7) against the New York Giants during the first half of an NFL football game in San Francisco, Sunday, Oct. 14, 2012.

Quarterback Alex Smith (11) during the second half. The San Francisco 49ers play the New York Giants at Candlestick Park in San Francisco, Calif., on Sunday October 14, 2012.

Photo: Stephen Lam, Special To The Chronicle

Quarterback Alex Smith (11) during the second half. The San...

Quarterback Alex Smith (11) during the second half. The San... Photo-3594494.49316 - SFGate

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Quarterback Alex Smith (11) during the first half of the San Francisco 49ers game agaisnt the New York Giants at Candlestick Park in San Francisco, Calif., on Sunday October 14, 2012.

Photo: Stephen Lam, Special To The Chronicle

Quarterback Alex Smith (11) during the first half of the San...

Quarterback Alex Smith (11) during the first half of the San... Photo-3594496.49316 - SFGate

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San Francisco 49ers quarterback Alex Smith (11) runs against New York Giants outside linebacker Michael Boley (59) during the first half of an NFL football game in San Francisco, Sunday, Oct. 14, 2012.

San Francisco 49ers quarterback Alex Smith (11) thows a pass away from New York Jets' Yeremiah Bell (37) as teammate Kendall Hunter (32) blocks during the second half of an NFL football game Sunday, Sept. 30, 2012, in East Rutherford, N.J. the 49ers won the game 34-0.

San Francisco 49ers running back Frank Gore, left, celebrates with teammate quarterback Alex Smith, right, after their team scored a touchdown during the second half of an NFL football game against the Minnesota Vikings Sunday, Sept. 23, 2012, in Minneapolis.

Colin Kaepernick shared a light moment near the end of the game with Michael Crabtree 15 and Carlos Rogers 22. The San Francisco 49ers defeated the Chicago Bears 32-7 at Candlestick Park Monday November 19, 2012.

Photo: Brant Ward, The Chronicle

Colin Kaepernick shared a light moment near the end of the game...

Colin Kaepernick shared a light moment near the end of the game... Photo-3807179.49316 - SFGate

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San Francisco 49ers' Alex Smith drops back to pass during the second half of an NFL football game against the Green Bay Packers Sunday, Sept. 9, 2012, in Green Bay, Wis. The 49ers won 30-22.

San Francisco 49ers' Randy Moss is congratulated by quarterback Alex Smith after Moss caught a touchdown pass during the first half of an NFL football game against the Green Bay Packers Sunday, Sept. 9, 2012, in Green Bay, Wis.

Matt Cain got a handshake from 49ers coach Jim Harbaugh as Alex Smith (left) looked on. The San Francisco Giants celebrated their second World Series title in three years with a parade down Market Street Wednesday October 31, 2012.

San Francisco 49ers quarterback Alex Smith, right, and Detroit Lions defensive end Kyle Vanden Bosch, left, are seen in action during the second quarter of an NFL football game in San Francisco, Sunday, Sept. 16, 2012.

San Francisco 49ers quarterback Colin Kaepernick (7) gestures after his second start in an NFL football game against the New Orleans Saints in New Orleans, Sunday, Nov. 25, 2012. The 49ers defeated the Saints 31-21.

Quarterback Colin Kaepernick #7 of the San Francisco 49ers runs the ball in for a touchdown against the New Orleans Saints at The Mercedes-Benz Superdome on November 25, 2012 in New Orleans, Louisiana.